1. Field of the Invention
The present invention is directed to a primary radiation diaphragm of the type used in a medical radiation application apparatus.
2. Description of the Prior Art
A primary radiation diaphragm is used in a medical radiation application apparatus to gate the x-ray beam emitted by a radiation source onto a desired region of a patient.
A primary radiation diaphragm as disclosed in German OS 20 53 089 having a plurality of diaphragm lamellae which are radially adjustable. These diaphragm lamellae are seated on a carrier plate which is disposed in a plane perpendicular to the central ray of the radiation beam. For adjusting the diaphragm lamellae, tangential guide channels are provided in the carrier plate and radial guide channels are provided in a set collar. The diaphragm plates have pins which engage these channels. When the set collar, which is seated on driven guide rollers, is rotated around its central axis relative to the carrier plate, the diaphragm lamellae are tangentially displaced, as a result of which the diaphragm aperture either enlarges or diminishes in size, dependent on the rotational direction of the collar.
Another primary radiation diaphragm is disclosed in European application 0 304 773 corresponding to U.S. Pat. No. 4,897,861, for an x-ray diagnostic apparatus, wherein two diaphragm plates are adjustable in plane perpendicular to the central ray of the x-ray beam. For gating the useful portion of the x-ray beam, the diaphragm plates, by appropriate adjustment, can form a slot or a V-shaped opening, with the slot or V-shaped opening lying either centrally or eccentrically relative to the central ray. The diaphragm plates are seated on a rotatable ring and have oblong holes into which pins of levers extend. The pins are displaceable within the oblong holes. The levers are seated so as to be rotatable around respective axes using an electric motor, so that the levers are pivoted, and thus the diaphragm plates are adjusted when the electric motors are driven. Because each lever is individually pivotable, the diaphragm plates can be adjusted not only radially relative to the central ray, but also obliquely relative to the central ray. The axes have potentiometers allocated to them which supply electrical signals corresponding to the positions of the levers, and thus corresponding to the adjustment of the diaphragm plates. These electrical signals are supplied to a control unit for the primary radiation diaphragm for processing.